Polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole

Abstract

We have studied the polarized image of an equatorial emitting ring around a 4D Gauss–Bonnet black hole. Our results show that the effects of Gauss–Bonnet parameter on the polarized image depend on the magnetic field configuration, the observation inclination angle, and the fluid velocity. As the magnetic field lies in the equatorial plane, the observed polarization intensity increases monotonously with Gauss–Bonnet parameter in the low inclination angle case, and its monotonicity disappears in the case with high inclination angle. However, as the magnetic field is vertical to the equatorial plane, the polarization intensity is a monotonously increasing function of Gauss–Bonnet parameter in the high inclination angle case. The changes of the electric vector position angle with Gauss–Bonnet parameter in both cases are more complicated. We also probe the effects of Gauss–Bonnet parameter on the Strokes Q–U loops.

Polarized Image of a Rotating Black Hole in Scalar–Tensor–Vector–Gravity Theory

“…Moreover, the analysis shows that the polarization patterns depend also on the strongly curved spacetime near the black holes. Thus, the study of polarized images of black holes is beneficial to probe the matter distribution and the related physical process around black holes (Connors et al 1980;Bromley et al 2001;Li et al 2009;Shcherbakov et al 2012;Dexter 2016;Gold et al 2017;Jiménez-Rosales & Dexter 2018;Marin et al 2018;Moscibrodzka 2020;Palumbo et al 2020;Gelles et al 2021;Moscibrodzka et al 2021;Narayan et al 2021;Qin et al 2021;Zhang et al 2021Zhang et al , 2022Hu et al 2022;Liu et al 2022;Zhu & Guo 2022), and even check theories of gravity.…”

“…Moreover, with this model, the image of a finite thin disk can be produced by simply summing contributions from individual radii. Thus, this model has been recently applied to study the polarized image of an equatorial emitting ring in various spacetimes, such as, 4D Gauss-Bonnet black holes (Qin et al 2021), regular black holes (Liu et al 2022), Schwarzschild-Melvin black holes (Zhu & Guo 2022), and so on.…”